Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $173.66   12.594%   $195.5307   $195.53   $195.55   $195.50  
  Purchase #2 $66.61   10.390%   $73.5308   $73.53   $73.55   $73.50  
  Purchase #3 $68.62   8.547%   $74.485   $74.49   $74.50   $74.50  
  Purchase #4 $97.46   11.218%   $108.3931   $108.39   $108.40   $108.40  
  Purchase #5 $209.56   12.700%   $236.1741   $236.17   $236.15   $236.20  
  Purchase #6 $212.32   9.286%   $232.036   $232.04   $232.05   $232.00  
  Purchase #7 $70.62   7.577%   $75.9709   $75.97   $75.95   $76.00  
  7 purchase totals = $898.85       $996.1206   $996.12   $996.15   $996.10